netdev - [PATCH v2 net-next 01/12] net: stmmac: Enable OSP for GMAC4

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Date:   Wed, 16 May 2018 13:50:43 +0100
From:   Jose Abreu <Jose.Abreu@...opsys.com>
To:     netdev@...r.kernel.org
Cc:     Jose Abreu <Jose.Abreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        Vitor Soares <Vitor.Soares@...opsys.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>
Subject: [PATCH v2 net-next 01/12] net: stmmac: Enable OSP for GMAC4

This enables OSP (Operate on Second Packet) for GMAC4. The feature
allows DMA to fetch second descriptor while its still processing the
first one.

Running iperf, the performance gain is +/- 38%.

Signed-off-by: Jose Abreu <joabreu@...opsys.com>
Cc: David S. Miller <davem@...emloft.net>
Cc: Joao Pinto <jpinto@...opsys.com>
Cc: Vitor Soares <soares@...opsys.com>
Cc: Giuseppe Cavallaro <peppe.cavallaro@...com>
Cc: Alexandre Torgue <alexandre.torgue@...com>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
index 117c3a5..9aab5b3 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_dma.c
@@ -94,6 +94,10 @@ static void dwmac4_dma_init_tx_chan(void __iomem *ioaddr,
 
 	value = readl(ioaddr + DMA_CHAN_TX_CONTROL(chan));
 	value = value | (txpbl << DMA_BUS_MODE_PBL_SHIFT);
+
+	/* Enable OSP to get best performance */
+	value |= DMA_CONTROL_OSP;
+
 	writel(value, ioaddr + DMA_CHAN_TX_CONTROL(chan));
 
 	writel(dma_tx_phy, ioaddr + DMA_CHAN_TX_BASE_ADDR(chan));
-- 
1.7.1